The front end was of a typical Garratt arrangement, with a water tank mounted on the front engine unit’s frame, while the rear end was constructed in the Modified Fairlie fashion, with the coal bunker mounted on a rigid extension of the locomotive’s main frame and with the pivoting rear engine unit positioned beneath the coal bunker.

The main frame therefore carried the smokebox, boiler, firebox, cab, coal bunker, as well as the underbelly water tank.

In the case of the Union Garratts, this occurred particularly at the rear, brought about by the long frame overhang laden with the coal bunker.

[3][4] Twenty-nine 4-6-2+2-6-4 Garratts, constructed between 1936 and 1941 by Société Franco-Belge in Northern France, operated until the Algerian independence war caused their withdrawal in 1951.

The Garratts were acquired in response to traffic growth over the heavy grades of the North Island Main Trunk and to eliminate the use of banking locomotives on steep gradients.

Collins, Chief Mechanical Engineer of the SAR from 1922 to 1929, who designed it as a mixed traffic locomotive for use on branch lines and secondary mainlines throughout the country.

[3][7] Six Garratt locomotives of this wheel arrangement, built by Euskalduna in 1931, were used on the 5 ft 6 in (1,676 mm) gauge Ferrocarril Central de Aragón (FCA) in Spain.

After the FCA was integrated into RENFE in 1941, the locomotives were converted to oil-burners and worked in the Tarragona-Valencia section on the line between Barcelona and Seville, until they were replaced by diesel traction in 1967 and retired.